So it’s been mentioned that Haruka possibly spends a lot of time sleeping over Makoto’s house and I can definitely see that being the case (whether he initially meant to or not) for the following reasons:
1- Haruka’s parents are a non-factor in his life, and it has been this way for a very long time. We know he’s currently living alone, and even in High Speed!, when he’s about 12 we never see his parents directly; the only time they’re even mentioned (to the best of my knowledge) is when Haruka is in the hospital. Even then we never see them arrive, we only hear Makoto tell Haruka that his mother is on her way.
2-Makoto tends to take on a lot of responsibilities, either out of necessity or because he thinks it’s a necessity. Enter Haruka, who has been in his life since kindergarten and doesn’t seem to have anyone taking care of him. It seems very natural to me that Makoto might’ve started inviting Haruka over out of a need to make sure he’s properly cared for, and it formed into a habit for both of them.
I’m not really sure if I had a point here other than saying I find their relationship really interesting with the potential for both bittersweet fluff and also a slightly darker interpretation (one translator mentioned that it seems like Makoto treats Haruka as an obsession, the same way he treats his pet goldfish).
Basically these boys man.